1. Field of the Invention
The present invention relates generally to braking systems and arrangements for trains traversing a track in a track network, and in particular to a method and system for determining the effectiveness of brake shoe mechanisms used in the braking arrangements during operation of the train.
2. Description of the Related Art
As is known in the art, in order to safety traverse a track in a track network, a train includes a complex braking arrangement for use in slowing and/or stopping the train in a variety of situations. Normally, the braking system on such trains is a pneumatically-driven arrangement having mechanisms and components that interact with each railroad car attached to the engine(s). A known braking arrangement BA is illustrated in schematic form in FIG. 1.
With reference to FIG. 1, the operator of the train TR also has control over the braking arrangement BA through the use of an operator control valve CV. Through the movement of a handle associated with the control valve CV, the operator can adjust the amount of braking to be applied in the braking arrangement BA (a measurement often referred to as braking force, and expressed in brake horsepower (HP-hr)). The higher the braking force selected, the faster the braking arrangement BA will attempt to slow and stop the train TR.
In order to provide the appropriately compressed air to the system, the braking arrangement BA also includes a compressor C for providing compressed air to a main reservoir MR, which is in communication with the control valve CV. Further, an equalizing reservoir ER is also in communication with the control valve CV. Whether through the main reservoir MR or the equalizing reservoir ER, compressed air is supplied through the control valve CV to a brake pipe BP that extends along and associated with each railcar. Each car includes an arrangement that allows an auxiliary reservoir AR to be charged with air via a valve V, as well as a brake cylinder BC that is in communication with the valve V. The brake cylinder BC is operable to urge a brake shoe mechanism BS against a surface of the wheel W. In addition, and due to the frictional contact between the brake shoe mechanism BS and the wheel W, a slack adjuster SA is in operable communication with the brake cylinder BC to ensure that appropriate contact is made between the brake shoe mechanism BS and the wheel W even as the brake shoe mechanism BS begins to wear.
In operation, the brake pipe BP is continually charged to maintain a specific pressure, e.g., 90 psi, and each auxiliary reservoir AR (as well as an emergency reservoir ER) is similarly charged from the brake pipe BP. In order to brake the train TR, the operator actuates the control valve CV and removes air from the brake pipe BP, thereby reducing pressure to a lower level, e.g., 80 psi. The valve V quits charging the auxiliary reservoir AR and transfers air from the auxiliary reservoir AR to the brake cylinder BC. Using a piston and lever arrangement, the brake cylinder BC urges the brake shoe mechanism BS against the wheel W. As discussed, the operator may adjust the level of braking using the control valve CV, since the amount of pressure removed from the brake pipe BP results in a specific pressure in the brake cylinder BC, which results in a specific application force of the brake shoe mechanism BS against the wheel W. Further, the force output of the brake cylinder BC is adjustable through use of the slack adjuster SA to ensure continuity in application force even under brake shoe mechanism BS wear conditions.
While the slack adjuster SA is effective in compensating for brake shoe mechanism BS wear, another major factor in determining the effectiveness (or the ability of the braking arrangement BA to provide sufficient retardation force to stop the train TR) of a brake shoe mechanism BS is fade. Brake shoe fade occurs through prolonged usage of the braking arrangement BA, since heat builds in the brake shoe mechanism BS and friction reduces, resulting in reduced performance. This brake shoe or friction fade is a key factor in determining the effectiveness of the braking arrangement BA to slow or stop the train TR in a variety of situations. Even with the use of electronically-controlled pneumatic braking arrangements, dynamic braking systems and the like, this fade has the potential to lead to the inability to brake the train TR with often catastrophic results.
As also known in the art, brake shoe fade can be calculated given the appropriate sets of data, and such predictive calculation of fade under certain situations is presently conducted using quantitative modeling techniques. Various tables have been developed that can be used to determine braking ratio, i.e., the application force at the wheel W based upon the pressure in the brake cylinder BC and train weight, as developed by the Association of American Railroads. Still further, specifications have been developed for determining brake shoe mechanism BS friction, as based upon the speed of the train TR and the application force. Using a dynamometer, a curve can be developed to demonstrate how temperature affects brake shoe mechanism BS performance. Finally, based upon this preexisting and determined data, brake shoe fade can be determined under specific and set conditions, and the railroad will then use the developed tables as one factor in setting speed limits for various sections of track based upon conservative estimates of the weight of the train TR, the grade of the track, etc.
However, such speed limits, as well as the estimated brake shoe fade, are developed based upon known or predetermined information and data. Additionally, it is necessary to establish speed limits in a conservative manner, which results in inefficiencies in the transport process and railroad logistics. Still further, such calculations cannot take into account dynamically changing conditions, and cannot be used to determine whether the train TR can slow to a specific speed level or be stopped. In particular, if the operator uses the braking arrangement BA for a significant period of time, brake shoe fade rises, and thereafter, after application has ceased, the brake shoe fade decreases (eventually to ambient)—which is often referred to as the “recovery time” of the brake shoe mechanism BS. Still further, these predetermined brake shoe fade and application force determinations do not account for environmental conditions, e.g., heat, snow, rain, etc.
Further, and in general, there exist different train control systems and methods for use in data calculation and/or controlling trains. For example, see U.S. Pat. No. 5,744,707 to Kull; U.S. Pat. No. 5,785,392 to Hart; U.S. Pat. No. 5,862,048 to Knight; U.S. Pat. No. 5,892,437 to Scheibe et al.; U.S. Pat. No. 6,263,266 to Hawthorne; U.S. Pat. No. 6,622,068 to Hawthorne; U.S. Pat. No. 6,648,422 to Root et al.; U.S. Pat. No. 6,739,675 to Scharpf et al.; U.S. Pat. No. 6,847,869 to Dewberry et al.; U.S. Pat. No. 7,034,480 to Kumar et al.; 7,073,753 to Root et al.; U.S. Pat. No. 7,117,137 to Belcea; and U.S. Pat. No. 4,692,867 to Poole. Also see U.S. Publication No. 2003/0200020 to Ring and an article entitled “Brake-by-Wire Comes to Freight Trains” by Robb Mandelbaum, published in IEEE Spectrum on page 18 of the February 2008 issue.
Therefore, there exists such prior art predictive models, but these models and systems exhibit various drawbacks and deficiencies in both development and implementation. Such prior art systems lead to logistical and other deficiencies in the railroad system, and in certain cases are incorrect based upon certain changing data, which results in derailments and other catastrophic results. Still further, many of these prior art systems and methods are amenable to further augmentation or beneficial functioning in order to provide dynamic modeling in operational conditions, and maintenance of safe conditions throughout the track network. Further, and as one would expect, the safe operation of a train is a necessity for protecting the operator, crew, motorists, pedestrians, etc.